This invention relates to the field of brachytherapy and the manufacture and handling of small radioactive seeds. Brachytherapy involves the implantation of small radioactive seeds, or pellets into tumors to eradicate cancerous cells, and is an alternative to external radiation therapy such as electron beam irradiation.
Brachytherapy has been used in the treatment of numerous types of cancer, including cervical, breast, lung, head and neck, and prostate. As an example of the procedure the treatment of prostate cancer will be used. This is in no way intended to limit the scope of this application, as the use of the invention disclosed herein has general application in the handling of the radioactive pellets, or seeds, as will be obvious to those skilled in the art.
The treatment of prostate cancer using radioactive seed implantation has been known for some time. Currently either Palladium-103 or Iodine-125 seeds are used, with apparent activities ranging from about 0.25 mcuries to 1.2 mcuries, depending on the prostate size and aggressiveness of the cancer. Recent advances in ultrasound imaging and other technological advancements have enabled this procedure to become a very viable alternative to other treatments such as external beam irradiation and radical prostatectomy. The procedure involves ultrasound mapping of the prostate gland and size of tumor using a transrectal ultrasound probe. A radiation oncologist will then decide on the number and positioning of the radioactive seeds needed to deliver a sufficient amount of radiation to kill the cancerous cells. The requisite number of radioactive seeds are typically loaded into 18 gauge brachytherapy needles. Needles may contain anywhere from one to seven seeds, usually separated by bio-absorbable spacers of catgut or other suitable suture material. To prevent the seeds and/or the spacers from falling out of the needle accidentally, the distal end of the needle, the tip, is plugged with a small amount of bone-wax. Bone-wax is a medical grade beeswax material. The seeds are prevented from falling out of the proximal or hub end of the needle by a blunt obturator, which is ultimately used to force the seeds from the 18 gauge needle once in position in the prostate. The needles are inserted into the prostate transperineally.
In a typical procedure the needles loaded with seeds are inserted into the prostate gland under the guidance of the ultrasound rectal probe. A metal grid, abutting the peritoneum, having X-Y coordinates is matched to a grid overlaid on the real-time ultrasound picture, so that the requisite number of seeds can be placed at each location in accordance with the mapping planes used by the radiation oncologist to optimize dose delivery. Once the tip of the needle is visualized in the correct location on the ultrasound screen, the needle is withdrawn over the obturator whilst maintaining the position of the obturator, such that a pattern of seeds and spacers is laid down as required. Typically about 85 seeds are placed during the procedure, but the number can be as high as about 140 or as low as about 40. Thus a typical procedure uses about 30 needles per patient.
Currently the seeds and the spacers are loaded into the needles by the radiation oncologist or radiation physicist by hand. This is a laborious task, and can take up to an hour to complete. This can tie-up Operating Room time, and at a minimum is wasting radiation oncologist or physicist time. Furthermore, during this time the person doing the loading is exposed to undesirable levels of radiation, and the loading task is extremely fatiguing. Some mechanical assist devices exist, but they are either unreliable, and can jam or, even worse, break or crush a seed allowing radioactive material to escape. In addition, verification of seed loading per needle is generally not readily accomplished. A system marketed by Northwest Radiation Therapy Products organizes the seeds, spacers, and needles on a stand. This lessens operator movement, but the process is still time consuming.
An alternate approach for delivering the seeds to the patient is typified by instruments called the Mick Applicator and the Quick Seeder Applicator sold by Mick Radio-Nuclear Instruments, Inc. In this system the empty needles are first inserted into the patient at the predetermined locations. Then using the Mick Applicator one seed at a time is delivered from a pre-loaded cartridge, indexing back a pre-determined distance after delivering each individual seed. In the case of the Quick Seeder Applicator, a cartridge pre-loaded with seeds and spacers is attached to the needle. This device transfers a column of seeds and spacers by indexing back a pre-determined distance to accomplish the delivery. Again the cartridges are loaded either by hand or by using a device that consists of a chamber in which the seeds and spacers are lined up before being pushed into the cartridge. This is time consuming because seeds and spacers still have to be hand loaded into the transfer chamber, thus offering little benefit over straight hand loading. The invention described herein overcomes the deficiencies in the prior art and provides an improved means for loading needles. No supplier provides pre-loaded needles for brachytherapy.
Another approach for delivering the seeds to the patient is typified by the RAPID Strand™ Rigid Absorbable Permanent Implant Device sold by Nycomed Amersham. This device consists of ten Iodine-125 seeds spaced at a fixed distance within a polyglactin 910 absorbable suture. The suture material containing the seeds is stiffened and then sterilized. RAPID Strand™ is implanted in the patient using standard implantation techniques and disposable needles. Disadvantageously, RAPID Strand™ frequently jams the implantation needle, requiring the implanting physician to discard the needle and seeds. Further, because RAPID Strand™ uses a bioabsorbable suture, once the body absorbs the suture, the seeds may migrate and not accomplish their intended purpose.
U.S. Pat. No. 5,928,130 by Schmidt describes a tool for implanting radioactive seeds that includes a needle, spacers and seeds loaded into a transparent or translucent sleeve, and an obturator to facilitate the displacement of spacers and seeds and deposit them into tissue.
Notwithstanding the various efforts in the prior art, there remains a need for a preloaded brachytherapy seed system as described in detail below.
Proper seed placement and seed retention at the implantation site strongly influence the success or failure of a brachytherapy procedure. As described above, seed implantation devices generally contain a plurality of seeds that may be separated by spacers. Prior implantation devices and methods do not reliably maintain proper seed spacing during and after implantation. Therefore, a device and/or method of reliably maintaining proper seed spacing during and after implantation would be of great benefit to brachytherapy patients.
Loose seeds, especially those that are extra-capsular (located outside the capsule of the prostate), tend to migrate within the patient. Because extra-capsular tissue is less dense than tissue within the capsule of the prostate, prior brachytherapy seed implantation devices and methods can not effectively maintain the location of seeds in the extra-capsular material. These seeds readily migrate and fail to provide radiation where needed. Migrating radioactive seeds not only fail to provide needed radiation therapy at the treatment site, but may cause damage to other radiation-sensitive areas of the body. Therefore, a device and/or method of preventing migration of radioactive seeds would be of great benefit to brachytherapy patients.